Triazine-Cored Lanthanide-Based Metal-Organic Frameworks Featuring Unique Water Chains and Strong Characteristic...

A new triazine-cored tricarboxylic acid, N,N',N"-1,3,5-triazine-2,4,6-triyltris(cis-4-aminocyclohexane-carboxylic acid) (H₃ L), has been prepared by replacing the chlorine atoms of cyanuric chloride with cis-4-aminocyclohexane-carboxylic acid, which has been used for the construction of a series of triazine-cored lanthanide-based metal-organic frameworks (MOFs). All these MOFs were structurally authenticated, revealing that they are isostructural and exist as two-dimensional (2D) coordination networks with the general formula [Ln(L)(H₂ O)₂ ]⋅5.5 H₂ O (Ln=1⋅Gd, 2⋅Tb, 3⋅Eu). A unique one-dimensional water chain, composed of primary tetrameric cyclic rings and dodecameric cyclic rings, has been found entrapped in the lattice. Moreover, all these compounds display bright characteristic photoluminescence. Particularly, for 1, apart from the strong blue emission peak (Φ_f =20.6 %) corresponding to the intraligand transition under near-UV excitation, the characteristic emissions of Gd³⁺ cation (Φ_f =5.0 %) were unexpectedly observed upon excitation at 273 nm.